The invention relates to a system for automatically de-actuating electrical swimming pool pumps and other electrical equipment associated with the operation of a swimming pool. More specifically, the invention relates to a method and apparatus for shutting down such equipment in response to a predetermined drop in the level of water in the swimming pool.
Modern swimming pools typically include a filtration system for cleansing the water of dirt, algae and other undesirable matter such as hair, grass, etc. Such filtration systems normally incorporate an electrically-powered pump which pumps the water from the pool through a diatomaceous earth or sand filter and then back into the pool. It is usually necessary to circulate the water in the pool in this manner for a certain period of time each day (the amount of time depending on such factors as the size of the pool, the temperature of the water and the amount of usage of the pool, among others) in order to prevent the accumulation of a layer of dust and dirt on the surface of the water and to inhibit the growth of algae. To this end, it is quite common to have the swimming pool pump turned on for a predetermined period each day by means of a timer-clock switch. Such a system has the advantage that the pool may be left unattended for a period of several days or weeks without fear that the pool will accumulate excessive amounts of dirt and algae. Thus, such systems are particularly advantageous in swimming pools located in the yards of single family residences where the owners may be away for extended periods on vacations and the like.
This automatic cycling of the circulation system on and off does, however, present a potential hazard. For example, should leak occur in the water conduits between the pump and the swimming pool on the outlet side of the pump, while the pool is left unattended, vast quantities of water may be drained from the pool through the leak when the pump cycles on automatically. Not only can this result in substantial damage to the area which is flooded by the water emanating from the leak, but also there is the chance that if the situation is allowed to persist, the pool may be pumped completely dry, thereby necessitating not only the troublesome operation of refilling the pool, but also subjecting the pool to the danger of cracks, requiring considerable expense to repair. Moreover, the timer-clock which cycles the pump on and off frequently performs the same function for the swimming pool underwater lights. These lights must be kept underwater at all times that they are in operation, inasmuch as contact with the water is required to prevent the lamps from overheating. Thus, a leak in the circulation system which caused the level of the water water in the pool to drop below the lamps could result in their destruction. Furthermore, if the leak results in the drainage of the pool, there would be no water flowing into the pump, which could result in substantial damage to the pump if it is allowed to run for any significant length of time in this condition.
It will readily be appreciated at this point that the above problems can occur not only in a swimming pool circulation system, but also with any system having a reservoir of liquid which is circulated by means of an electrical pump. Thus, the need has been established in such systems for means of de-actuating, in response to a predetermined drop in the level of liquid in the pool or reservoir, the pump or other electrical apparatus which may cause or suffer damage if the level of liquid drops below a predetermined level.